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This wikiHow teaches you how to install a power supply for a Windows desktop computer. The power supply is what facilitates the flow of power from an electrical source to the other components of the computer. Keep in mind that if your computer came pre-assembled, you don't need to install the power supply, though you may eventually need to replace it.

Find a power supply for your computer. The power supply that you buy depends on the computer's motherboard and housing size, meaning that you'll need to research your motherboard model to see which power supplies will fit. You can usually find power supplies in tech departments or stores, as well as in online shops like Amazon and eBay.

Make sure that you buy a power supply that is optimized for your region. Power supplies for European markets use different voltage settings than the ones used in North American markets.

Assemble your tools. You'll need at least one screwdriver (typically a Phillips head) to open the CPU housing, which is usually the right-hand side of the CPU box when looking at the back of the box. You may need a different screwdriver for your power supply as well—look at the screws that came with the power supply to determine whether or not this is the case.

Set the power supply's voltage switch. If there's a voltage switch on the power supply, switch it to the 110v or 115v setting. This will ensure that your power supply provides ample power without damaging the components to which it's connected.

Not all power supplies have voltage switches, and those that do normally have the switch set to the standard of the region for which they were purchased.

Insert the power supply. The power supply should have a distinct "back" with plugs and a fan, as well as a "bottom" with a fan on it. The "back" should face the back of the case, while the "bottom" should face the internal part of the case.

Attach the power supply to the motherboard. Find the main power cable on the power supply (usually the one with the largest plug) and attach it to the long, rectangular port on the motherboard, then attach the secondary power cable to the motherboard.

Depending on your power supply and motherboard, you may not have a secondary power cable.

The plug used to attach the power supply to the motherboard is usually a 20- or 24-pin connector.

Connect the power supply to other computer components. Using the smaller cables, connect the power supply to your computer's hard drive, CD drive, and graphics card. If you have other components in your case (e.g., a lighting system), you may need to plug these in as well.[1]XResearch source

Turn on your computer. If everything is connected and powered properly, the fan on the power supply should turn on and your computer will boot like usual. If you hear a beep and nothing happens, then something inside is not connected correctly, or the power supply is not providing enough power to your components.[2]XResearch source

You can either buy a PSU tester or take a paper clip and fold it into a U-shape. On the 20/24 pin power cable, put one end of the paper clip in the slot that the green wire runs into. Then put the other end in the slot that any black wire runs in. Plug the PSU into a wall plug, and flip the switch on.

It depends on whether you want the power supply to affect the air pressure of the machine. If you want to have a more negative air pressure, aim the fan into the case. However, this could lead to a slight temp increase for the PSU, which could, in turn, mean louder operation.

Usually a 450w power supply will be able to work with a GPU that requires 500w. 450w power supplies are usually rated to go up to around 500w. The 500w on the GPU specifications is usually to avoid people from using extremely under powered PSU.

If your hard drive doesn't have a Molex power connector (as is the case with most or all modern hard drives), you can use a Molex-to-SATA adapter. Check to see if your power supply already has a SATA power connector first, though.

Warnings

Remember that all power supplies contain various capacitors inside of them that retain power even after it has been turned off. Never open up or insert any metal objects into the vents of it, as you can risk electrical shock.

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